Heretofore, for example, in the diagnosis or the like of infectious diseases, sample analysis tools for detecting antigens of pathogens such as bacteria and viruses utilizing an immunoreaction are in widespread use. In such sample analysis tools, immunochromatography (an immunoassay method) is used widely. The immunoassay method is one technique for conducting analysis using substances that specifically bind to an analyte such as the above-described antigen (specifically binding substances). According to the immunoassay method, it is possible to conduct analysis easily and rapidly. In recent years, an immunoassay method in which an enzyme is used as a label (an enzyme immunoassay method) has been developed (see Patent Document 1, for example).
The enzyme immunoassay method is carried out in the following manner, for example. Specifically, first, a sample is collected from a nasal cavity or the like, and a sample solution containing the sample is prepared. On the other hand, a sample analysis tool is provided. FIGS. 6A and 6B show an example of the sample analysis tool. FIG. 6A is a plan view of the sample analysis tool. FIG. 6B is a sectional view of the sample analysis tool, viewed along arrows III-III in FIG. 6A. In FIGS. 6A and 6B, common components and portions are given the same reference numerals. In the sample analysis tool 60, a developing solution supply portion 62, a sample supply portion 63, and a detection portion 64 are provided in a porous development member 61 in this order from upstream to downstream along the flow of a developing solution (from the right to the left in FIGS. 6A and 6B). In the detection portion 64, an antibody is immobilized (immobilized antibody).
First, the sample solution is supplied to the sample supply portion 63. Next, a developing solution is supplied to the developing solution supply portion 62. By the development of the supplied developing solution in the development member 61 in the presence of a labeled antibody labeled with an enzyme (an enzyme-labeled antibody), the supplied sample solution is introduced into the detection portion 64. Furthermore, by the development of the supplied developing solution, a substrate is introduced into the detection portion 64 from the developing solution supply portion 62 via the sample supply portion 63. FIG. 6C is a schematic view showing an example of the detection of an antigen in the detection portion 64. In FIG. 6C, the same components and portions as those in FIGS. 6A and 6B are given the same reference numerals. As shown in FIG. 6C, when an antigen 66 as an analyte is present in the sample, a complex 68 of the enzyme-labeled antibody 65, the antigen 66, and the immobilized antibody 67 is formed in the detection portion 64. In this state, by detecting the color development, light emission, or the like caused by the reaction of the enzyme 69 of the enzyme-labeled antibody 65 in the complex 68 with the substrate, the antigen 66 is detected.